#include <iostream>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

// void ChildWrite(int wfd)
// {
//     char buffer[1024];
//     int cnt = 0;
//     while(true)
//     {
//         // snprintf为C语言接口，自带\0，不需要-1
//         snprintf(buffer, sizeof(buffer), "I am child, pid: %d, cnt: %d", getpid(), cnt++); 
//         write(wfd, buffer, strlen(buffer));
//         sleep(2);
//         //break;
//         //sleep(1);
//     }
// }

void ChildWrite(int wfd)
{
    char c = 0;
    int cnt = 0;
    while(true)
    {
        write(wfd, &c, 1);
        printf("child: %d\n", cnt++);
    }
}

void FatherRead(int rfd)
{
    char buffer[1024];
    int cnt = 0;
    while(true)
    {
        //sleep(5);
        sleep(100);
        buffer[0] = 0;
        // read为系统接口，需要-1
        ssize_t n = read(rfd, buffer, sizeof(buffer)-1);
        if (n > 0)
        {
            buffer[n] = 0;
            std::cout << "child say: " << buffer << std::endl; 
            //sleep(2);
        }
        else if (n == 0)
        {
            std::cout << "n: " << n << std::endl;
            std::cout << "child退出,我也退出" << std::endl;
            break;
        }
        else
        {
            break;
        }
        //break;
    }
}

int main()
{
    // 1. 创建管道
    int fds[2] = {0}; // fds[0]: 读端  fds[1]: 写端
    int n = pipe(fds);
    if (n < 0)
    {
        std::cerr << "pipe error" << std::endl;
        return 1;
    }
    std::cout << "fds[0]:" << fds[0] << std::endl;
    std::cout << "fds[1]:" << fds[1] << std::endl;

    // 2. 创建子进程
    pid_t id = fork();
    if (id == 0)
    {
        // 子进程
        // 3. 关闭不要的读写端，形成通信信道
        // 子进程写，关闭读端
        close(fds[0]);
        ChildWrite(fds[1]);



        close(fds[1]);
        exit(0);
    }

    // 3. 关闭不要的读写端，形成通信信道
    // 父进程读，关闭写端
    close(fds[1]);
    FatherRead(fds[0]);
    close(fds[0]);

    sleep(5);
    int status = 0;
    int ret = waitpid(id, &status, 0);
    if (ret > 0)
    {
        printf("exit code:%d, exit signal:%d\n", (status>>8)&0xFF, status&0X7F);
        sleep(5);
    }
    return 0;
}